1. Field of the Invention
The present invention relates to a drive control technique of a power system including fuel cells.
2. Description of the Related Art
Various power systems have been developed and proposed, which include fuel cells and a fuel gas generation system for generating a fuel gas to be supplied to the fuel cells and output electric power. In some type of the known fuel gas generation systems, a reformer reforms a material like gasoline or methanol to produce a hydrogen-containing gaseous mixture and a hydrogen separator unit with a hydrogen separation membrane extracts hydrogen from the gaseous mixture.
In this known fuel gas generation system with the hydrogen separation membrane, some techniques of removing hydrogen from the hydrogen separator unit at a stop of the system have been proposed to prevent hydrogen brittleness of the hydrogen separation membrane (for example, see Patent Laid-Open Gazette No. 2001-118594 and No. 2002-93449).
Application of the power system to mobile objects, such as vehicles with a motor as a driving source, has been highly expected. On the vehicle, however, the fuel gas generation system is subjected to frequent temporary stops, for example, during a stop at a traffic light and during a drive on a downslope. Removal of hydrogen from the hydrogen separator unit at every temporary stop undesirably lengthens a restart time of the system and causes a significant energy loss.
As described in Patent Laid-Open Gazette No. 2001-35518, a hydrogen reservoir may be placed in the fuel gas generation system to warm up the fuel gas generation system and quickly supply hydrogen to the fuel cells at the time of a restart of the fuel gas generation system. The presence of the hydrogen reservoir, however, undesirably increases the size of the whole system and complicates the system configuration.